[binutils-gdb] [AArch64] Fix pseudo-register numbering in the presence of unexpected additional registers

[binutils-gdb] [AArch64] Fix pseudo-register numbering in the presence of unexpected additional registers

[Luis Machado]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1ba3a3222039eb2576d29c9fd3af444f59fa51d2

commit 1ba3a3222039eb2576d29c9fd3af444f59fa51d2
Author: Luis Machado <luis.machado@arm.com>
Date:   Fri Sep 9 10:30:53 2022 +0100

    [AArch64] Fix pseudo-register numbering in the presence of unexpected additional registers
    
    When using AArch64 GDB with the QEMU debugging stub (in user mode), we get
    additional system registers that GDB doesn't particularly care about, so
    it doesn't number those explicitly.
    
    But given the pseudo-register numbers are above the number of real registers,
    we need to setup/account for the real registers first before going ahead and
    numbering the pseudo-registers.  This has to happen at the end of
    aarch64_gdbarch_init, after the call to tdesc_use_registers, as that
    updates the total number of real registers.
    
    This is in preparation to supporting pointer authentication for bare metal
    aarch64 (QEMU).

Diff:
---
 gdb/aarch64-tdep.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index d0387044934..76e039a7d5f 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -3598,8 +3598,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   tdep->jb_elt_size = 8;
   tdep->vq = vq;
   tdep->pauth_reg_base = first_pauth_regnum;
-  tdep->ra_sign_state_regnum = (feature_pauth == NULL) ? -1
-				: ra_sign_state_offset + num_regs;
+  tdep->ra_sign_state_regnum = -1;
   tdep->mte_reg_base = first_mte_regnum;
   tdep->tls_regnum = tls_regnum;
 
@@ -3698,6 +3697,18 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 
   tdesc_use_registers (gdbarch, tdesc, std::move (tdesc_data));
 
+  /* Fetch the updated number of registers after we're done adding all
+     entries from features we don't explicitly care about.  This is the case
+     for bare metal debugging stubs that include a lot of system registers.  */
+  num_regs = gdbarch_num_regs (gdbarch);
+
+  /* With the number of real registers updated, setup the pseudo-registers and
+     record their numbers.  */
+
+  /* Pointer authentication pseudo-registers.  */
+  if (tdep->has_pauth ())
+    tdep->ra_sign_state_regnum = ra_sign_state_offset + num_regs;
+
   /* Add standard register aliases.  */
   for (i = 0; i < ARRAY_SIZE (aarch64_register_aliases); i++)
     user_reg_add (gdbarch, aarch64_register_aliases[i].name,